Modern integrated circuits (ICs) are often required to operate at frequencies well within the gigahertz range. With respect to frequencies of 10 GHz or less, a variety circuit structures are known to provide acceptable performance. Known inductor-capacitor (LC) circuit structures, for example, can be implemented that operate at 10 GHz or less with a suitably high quality (Q) factor. These LC circuit structures incorporate finger capacitors.
The Q factor of a circuit generally decreases as frequency increases. As frequencies increase beyond 10 GHz, performance of conventional LC circuit structures begins to degrade markedly. As an example, the Q factor of a conventional LC circuit structure that utilizes finger capacitors can be expected to decrease by as much as 67 percent when frequency is increased from approximately 10 GHz to approximately 32 GHz.
Techniques for improving the Q factor of an LC circuit structure at such high frequencies have included increasing the width of the bus line of the finger capacitors, increasing the width of the finger elements of the finger capacitors, or both. These techniques, however, consume significant area thereby reducing the area available within the IC for other circuitry and/or increasing the size of the IC itself. Further, increased widths of the bus line and/or finger elements increases parasitic capacitances in the LC circuit structure. Increased parasitic capacitance can degrade the tuning range of circuits such as voltage controlled oscillators and/or other circuits that typically rely upon or incorporate the LC circuit structure.